The small free-living soil nematode Caenorhabditis elegans may be a good biological model for studying the genetic basis of aging (and development generally) because of its suitability for genetic methods, its relative cellular simplicity, and its short lifespan. This proposal has two overall objectives. The first is the development and demonstration of an efficient method for generating somatic mosaics of C. elegans. The proposed method makes use of free and translocated chromosomal duplications that are mitotically unstable. Mosaic animals could prove useful in ascertaining the cell autonomy and tissue specificity of gene expression. The second overall objective is to identify by mutation genes in C. elegans whose functions affect general recombination ability, spontaneous and induced mutabilities, meiotic chromosome disjunction, sensitivities to radiation and mutagens, and mitotic loss of duplications. These properties, which are generally concerned with chromosome integrity and which may be important in cellular aging, have been shown in other organisms to be related; therefore, mutants identified on the basis of one property will be tested with respect to all other properties.